Tithonia rotundifolia aka Mexican Sunflower

Tithonia rotundifolia belongs to the aster family. Its common name is Mexican sunflower. It comes from Mexico and Central America. The climate there is tropical, with a dry season. This annual grows fast, with tall, upright stems that branch. Garden plants often reach 3–6 feet [0.9–1.8 metres]. RHS gives a taller range, reaching 8.2 feet [2.5 metres]. Spread varies between sources, from 0.3–3 feet [0.1–0.9 metres]. Its height suits a spot behind shorter border plants.

The green leaves grow by turns along the stems. Each simple leaf has an oval or triangular shape. Some leaves have three lobes. Leaf edges have sharp teeth or round scallops. The leaf surface feels rough, with hairs beneath it. Leaves reach 0.25–1 foot [0.08–0.3 metres] long. The straight stems have angles, slight ridges, and hairs. Their colour ranges from green to brown. The plant forms a bush and sheds its leaves.

Bright flower heads bloom from July into autumn. Orange to red ray flowers ring the yellow-orange disc flowers. Each head can reach about 0.26 feet [0.08 metres] across. The blooms draw bees, butterflies, and hummingbirds to the garden. Birds also visit the plant. Remove spent heads to help it bloom for longer. Grow the flowers for cutting or use in indoor displays. Brown fruits called achenes form after the flowers. They grow in round, spiky clusters. Each fruit measures less than 0.08 feet [0.025 metres] across.

Give this plant full sun and soil that drains well. It grows in clay, loam, sand, and shallow rocky ground. It accepts acid, neutral, and alkaline soils. NC State notes that it grows well in poorer soil. RHS advises soil with a fair level of nutrients. It also calls for shelter from strong winds. Tall plants may need stakes to keep them upright. It copes with heat, drought, and dry ground. Still, give it water during dry spells. Cool, cloudy weather can limit growth. RHS rates it H2; it will not survive freezing.

Use Mexican sunflower in informal beds and gravel gardens. It also suits wildlife gardens. It gives seasonal screening and colour behind a border. Start seeds with gentle warmth in spring. Sow outdoors once the last frost has passed. It needs little routine care, and serious pests are rare. Slugs and snails can harm young shoots. Sources report few disease problems and some resistance to deer.